(1) Field of the Invention
The invention relates to an actuating device for a gear-changing transmission, for example for a gearbox or for an automatic transmission with shift-by-wire actuation, according to the preamble of claim 1.
(2) Description of Related Art
Gear-changing transmissions for automobiles are generally shifted or controlled with an operating device arranged within the reach of the operator. Typically, actuating elements, such as shift levers or selection levers, are used which are arranged, for example, between the front seats of the automobile or in other areas of the cockpit.
In particular, ergonomic and safety reasons demand that presently impermissible shift positions or the execution of the demanded shifting actuation, is haptically indicated to the operator in form of corresponding shifting resistances or interlocks on the shift lever. Only in this manner can a haptic shifting actuation be realized, like an actuation the operator is familiar with or used to, for example from fully synchronized mechanical gearboxes with their rotation-speed and vehicle-speed dependent synchronized interlocks, or from the conventional actuation of an automatic transmission with its locking mechanism and its gear shift locks.
It is therefore always necessary to transmit to the operator during actuation of the transmission an unambiguous tactile feedback about the actual shift or operating state of the transmission or about the shifting success.
However, with electrical or shift-by-wire actuation of gear-changing transmissions, there is no longer a mechanical coupling between the shift lever in the passenger compartment and the automobile transmission in the engine compartment. Instead, the shift commands in the “shift-by-wire” transmission are transmitted from the actuating device to the automobile transmission by way of electrical or electronic signals and subsequent predominantly electro-hydraulic conversion of the shift commands on the transmission.
Due to the absence of a mechanical linkage between the transmission actuators and the actuating lever, the state of the transmission, any gear shift locks or impermissible shift commands can no longer provide direct feedback about the position of the actuating lever so as to be perceptible by the operator.
With shift-by-wire-controlled transmissions, the driver is therefore unable to easily recognize, based on certain shift positions which are perceptibly blocked on the shift lever, that shift lever positions, gear positions and/or shift commands may not be allowed under the current driving conditions and should therefore also not be selected. Likewise, with shift-by-wire actuation, the actual execution of the operator's shift commands by the transmission is also not fed back to the shift lever, so that the operator is unable to haptically sense the execution of the shifting actuation in the same way he is used to, for example, from mechanically operated gearboxes with their locking mechanism and gear synchronizing locks.
Depending on the state of the gear-changing transmission to be operated and depending on other conditions on the automobile—e.g., engine rpm, vehicle speed, clutch position, etc.—, it is therefore necessary for realizing the required haptic feedback with shift-by-wire-controlled transmissions to limit or delay the movement of the shift lever under active control or to generally introduce actuating forces into the lever—much like a Force Feedback.
Only in this way can the operator receive haptic feedback with a shift-by-wire-controlled transmission, when he touches the actuating lever, indicating that the desired gear shift is not permitted—for example, based on the actual vehicle speed or based on a current operating state of the gear-changing transmission—and is therefore blocked. This can prevent impermissible shift commands, which are recognized by the electronics unit of the transmission and therefore not transmitted from the operating device to the transmission, from being engaged on the shift lever.
As seen from the example described in DE 10 2005 001 589 B3, it is known in the state of the art to implement the haptics corresponding to an actuating element with mechanical force transmission in a shift-by-wire switched gear-changing transmission by providing the actuating element with an electronically controllable blocking actuator. The blocking actuator is controlled with a control device so that currently impermissible shift states are noticeably blocked and can therefore not be selected by the operator.
However, such actuating devices with blocking actuators are not optimal for providing a realistic haptic experience, because the actuating lever can only be either completely blocked by the blocking actuator or completely unblocked. A more realistic haptic which better corresponds to a mechanical force transmission to the gear-changing transmission—in particular with respect to force feedback—cannot be accomplished with the conventional use of blocking actuators. It is merely haptically transmitted to the operator on the shift lever that the shift lever is either freely movable (blocking actuator deactivated), or that certain switch positions are completely blocked (blocking actuator activated).
In particular, conventional blocking actuators are unable to provide gradual haptic signaling (which increases with the excursion) of actual blocking of a certain shift position—depending on the traveled distance of the hand of the operator on the switch lever—, because the conventional blocking actuators only recognize two states, namely “actuating position blocked” or “actuating position unblocked.”
On the other hand, conventional actuating devices with force feedback frequently have disadvantages because the components required for realizing the force feedback must generally be mounted as an additional assembly in the region of the actuating lever or in the housing of the actuating device. This increases the structural complexity and requires separate installation space which is frequently not available in view of the increasingly smaller actuating elements for modern automobile transmissions. In addition, conventional force feedback devices always require a dedicated actuator drive which not only requires additional space, but also consumes additional energy and hence produces more heat.